Thermoplastic polymers, e.g., polyamides, polyesters, polyphenylene sulfide, polyoxymethylene, polyolefins, styrene polymers and polycarbonates, are characterized as exhibiting exceptional mechanical and electrical properties as well as good moldability and chemical resistance. However, these polymers may exhibit inadequate tribological properties when utilized in some frictional environments, e.g., plastic to metal, and plastic to plastic interfaces. While many lubricating compositions have been applied to thermoplastic polymers to improve friction and wear properties, certain applications prohibited the use of many desirable lubricants because of possible contamination, e.g., food handling, clothing preparation, and volatile environments.
Attempts have been made to improve the friction properties and reduce the surface wear of articles prepared from thermoplastic polymers by incorporating lubricants directly into thermoplastic polymers prior to the fabrication of shaped articles therefrom. Many materials in different combinations, including solid lubricants and fibers (e.g., graphite, mica, silica, talc, boron nitride and molybdenum sulfide), paraffin waxes, petroleum and synthetic lubricating oils, and polymers (e.g., polyethylene and polytetrafluoroethylene), have been added to thermoplastic polymers to improve the lubricating properties.
However, the addition of many of these additives in various combinations to thermoplastic polymers, while improving tribological properties have reduced other desirable physical and mechanical properties. Some lubricants have proven satisfactory for short terms at low speeds and loads, however, desirable friction properties of many of these lubricants significantly deteriorate over long periods of time under increased loads.
There is a desire for thermoplastic compositions possessing surface wear resistance and low friction properties under increasing loads over long periods of time. A suitable composition, when fabricated into a shaped article, should maintain the desired mechanical and physical properties long associated with thermoplastic polymers, and be non-contaminating when utilized in food handling and clothing manufacturing industries.